1. Field of the Invention
The invention relates to methods and to computer-aided motion compensation in a digitized image.
2. Description of the Related Art
Such a method and system are known from K Uomori, A. Morimura, H. Ishii, Electronic image stabilization system for video cameras and VCRs, SMPTE Journal, Vol. 101, No. 2, pages 66–75, 1992. In this known method, an image is recorded by a camera, is digitized and is stored. The recorded digitized image has pixels which have associated coding information. The expression coding information means brightness information (luminance information) or color information (chrominance information).
The stored image is enlarged, and the coding information is interpolated between the original pixels in the unenlarged image. “Global” motion estimation, that is to say estimation of the motion of the entire image, and “global” motion compensation are applied to the entire enlarged image. Global motion estimation results in the formation of an image motion vector, which is associated with the enlarged image. A motion-compensated image detail is read from the enlarged image. The expression motion-compensated image detail means an image detail which has been shifted by the determined image motion vector within the enlarged image.
The motion compensation is carried out in order to compensate in particular for a jittering motion of a person when recording an image using a handheld camera.
The procedure known from Uomori, et al. has the particular disadvantage that the enlargement of the image reduces the image resolution of the camera, and this is perceptible as blurring in the motion-compensated image.
It is also known for mechanical means to be used for motion compensation. In an arrangement such as this, mechanical sensors are provided in a camera and measure any motion, for example a jittering motion, to which the camera is subject. A moving lens system is also provided which is controlled as a function of the determined motion such that the motion is compensated for, thus ensuring a stable, motion-compensated image before the image is actually recorded.
However, this technology has the disadvantage that it is considerably heavier due to the additional sensors and due to the lens system. Furthermore, the production of such system is expensive. This technology is therefore unsuitable, especially for small appliances, for example a mobile video telephone.
A block-based image coding method is known in accordance with the H.263 Standard from ITU-T, International Telecommunication Union, Telecommunications Sector of ITU, Draft ITU-T Recommendation H.263, Videocoding for low bitrate communication, May 2, 1996. Further methods for global motion estimation are known from S. B. Balakirsky, R. Chellappa, Performance characterization of image stabilization algorithms, Proc. Int. Conf. On Image Processing, Vol. 2, 3, pages 413–416, 1996, R. Gupta, M. C. Theys, H. J. Siegel, Background compensation and an active-camera motion tracking algorithm, Proc. Of the 1997 Int. Conf on Parallel Processing, pages 431–440, 1997 and D. Wang, L. Wang, Global Motion Parameter Estimation Using a Fast and Robust Algorithm, IEEE Trans. On Circuits and Systems for Video Tech., Vol. 7, No. 5, pages 823–826, 1997.